In 3GPP, setting up a home base station (Home eNB; referred to, herein after as “HeNB”) for indoor use and constructing a closed subscriber group (CSG) cell is being discussed. As shown in FIG. 17, the CSG cell is constructed within a cell (macro-cell) constructed by ordinary base stations (eNB). Unlike the eNB, the HeNB is provided with a function enabling restriction of terminals (user equipment; referred to, hereinafter, as “UE”) that are permitted access, and a UE can only connect to a HeNB for which access permission is granted. Excluding emergencies, the UE is unable to connect without access permission regardless of a HeNB with high reception quality being detected.
To check access permission for a HeNB, the UE is required to check cell identification information included in notification information transmitted from the HeNB. Each CSG cell has an ID, referred to as a CSG ID, in group units, and access permission is granted to the UE in CSG ID units. The UE collates a CSG ID list (access permission list: white list) of accessible CSG cells, notification of which has been received from a network, and the CSG ID that is the cell identification information received from the notification information of the CSG cell, and judges that access is possible if the CSG ID of the detected CSG cell is included in the white list.
The HeNB connects to a gateway referred to as a HeNB gateway (written as “HeNB GW” in FIG. 17), or a mobility management device (mobility management entity; referred to, hereinafter, as “MME”). The MME secures network resources and manages NAS messages, such as a position registration message. Because the pieces of information in the white list are information on individual terminals, in view of security, the HeNB, assumed to be owned by each household, does not have the information in the white list. On the other hand, the MME can have the white list because it is managed by an operator.
All cells have cell identification information referred to as a physical cell ID (PCI). Regarding the CSG cell, as shown in FIG. 18, CSG cells having the same PCI may be present near a serving cell to which the UE is currently connected. This is referred to as a PCI collision. The UE measures reception quality for signals from near-by cells, and a trigger is generated when the reception quality of a near-by cell satisfies certain conditions. This is referred to as an event trigger. When the trigger is generated, the UE notifies the serving cell of the PCI of the cell having high reception quality using a measurement result report message (measurement report).
Based on the reception quality information, the serving cell decides a handover destination, and transmits a handover request message (handover request; HO request) to the handover destination cell. In this instance, if a PCI collision occurs, the serving cell may transmit the handover request message to the wrong cell. This is referred to as PCI confusion.
To prevent PCI confusion, the UE detects a cell global ID (CGI) that is a unique cell identifier from a notification message of the CSG cell, and notifies the serving cell of the CGI using the measurement result report message. As a result, the serving cell specifies the CSG cell. However, because time is required for CGI detection, first, notification is given of the PCI of the cell having high reception quality and the measured reception quality by a first measurement result report message (1st measurement report). The serving cell selects one handover destination candidate cell from the CSG cells within the received first measurement result report message and, to instruct the UE to detect the CGI of the CSG cell, transmits a measurement setting message (measurement configuration) including the PCI of the CSG cell and setting information required for detecting the CGI to the UE.
The UE performs CGI detection of the CSG cell of which instruction has been given based on the measurement setting message, and notifies the serving cell of the detected CGI by a second measurement result report message (2nd measurement report). A sequence of the above-described operation is shown in FIG. 19.